The present invention relates to a unit for making pre-shaped absorbent pads for sanitary items.
In particular, the present invention relates to a unit of the above-mentioned type which can advantageously be used for the production of diapers, sanitary towels and similar items.
The following description refers, without limiting the scope of the invention, to units for making pre-shaped absorbent pads for diapers.
As is known, diapers contain an absorbent pad which is normally sealed between an inner permeable layer of spun-bonded material and an impermeable polyethylene outer layer.
In the past, absorbent pads for diapers were relatively thick and were obtained by cutting into sections a continuous web consisting of a collection of absorbent material, normally cellulose fiber. Then, in response to new market demands, diaper manufacturers began to make anatomically shaped diapers. This meant that the pads had to be shaped, according to the desired anatomical shape, before being sealed between the above-mentioned inner and outer layers.
For a lengthy period the best solution consisted in the use of a pad forming drum, the outside of which was equipped with a plurality of vacuum seats shaped according to the desired anatomical shape for the pad, said outer surface being fed with absorbent material. A forming drum of the above-mentioned type is known, for example, from U.S. Pat. No. 4,674,966.
However, in recent years, on one hand the market demand has been for diapers with pads that are increasingly thin and absorbent, and on the other, diaper manufacturers requested increasingly fast production units. This led to a gradual reduction in the depth of the shaped vacuum seats and, at the same time, an increase in the peripheral speed of the above-mentioned forming drums.
The reduction of diaper pad thickness to extremely low levels and the improvement in diaper absorption were made possible by using super-absorbent materials inserted, according to a multi-layer structure, between layers of the collection of cellulose fiber. An absorbent pad of the aforesaid multi-layer type is known, for example, from U.S. Pat. No. 5,919,178.
The increase in the peripheral speed of the forming drums is obtained by increasing both the angular velocity of rotation and the external diameter of the drums. The increase in the angular velocity was possible up to a speed limit beyond which it was found that the layers of super-absorbent material and collections of cellulose fiber, subjected to excessive centrifugation, tended to break up and penetrate one another. Moreover, the increase in external diameter made the forming drums increasingly bulky, heavy and expensive.
The aim of the present invention is to provide a unit for making pre-shaped absorbent pads for sanitary items, such as diapers, sanitary towels or similar products, with a relatively high production speed and, at the same time, free of the disadvantages indicated with reference to the prior art.
Accordingly, the present invention provides a unit for making pre-shaped absorbent pads for sanitary items. The unit comprises conveyor means defining at least one line for the formation and feed of said absorbent pads and at least one absorbent material feed station located along the forming and feed line. The conveyor means comprise a plurality of seats evenly distributed along the forming and feed line. The seats are designed to accept and retain a given quantity of the absorbent material; wherein the conveyor means comprise a continuous conveyor belt, which has at least one operating branch defining the forming and feed line. The operating branch extends along a straight path and moves at a given speed and in a given direction.